The present invention related to a method of storing data on recording tape, the method employing helical scan recording in which data is written in oblique tracks. In particular, but not exclusively, the invention relates to a method of updating tape usage data held in a log area of the tape, this updating being effected at the end of each session of use of the tape.
Where data is stored by longitudinal recording on a tape, it is known to provide a log area for storing the tape usage data and to repeatedly update this data by rewriting the log area. The process is facilitated by the fact that the tape is generally recorded with formatting keys (usually fixed-frequency tones) dividing up the data, these keys either being pre-recorded or being written at the same time as the data. The log area will therefore be delimited by formatting keys and is generally read/written immediately following a particular key.
In the field of helical scan recording, a number of problems exist that are not present in longitudinal recording. In particular, it normally takes a number of tracks for the helical-scan recording head to become synchronized to any new sequence of tracks so that discontinuities in track pattern, such as will generally occasioned by over-writing old data with new, cause particular difficulties.
One object of the present invention is to provide a method for updating specified data tracks in tape written using helical scanning.